In-plane switching mode liquid crystal display device

ABSTRACT

An in-plane switching mode liquid crystal display device includes a substrate; at least two gate lines disposed on the substrate; at least two data lines disposed on the substrate crossing the gate lines to define a pixel region; a driving device disposed in the pixel region; a plurality of first electrodes disposed in the pixel region; and a plurality of second electrodes disposed in the pixel region parallel with the first electrodes. At least one first electrode is overlapped with at least one second electrode. Further, each one of the first electrodes and a corresponding one of second electrodes defining an electric field in a direction parallel to a surface of the substrate.

This application is a continuation of application Ser. No. 11/090,946,filed Mar. 28, 2005, now U.S. Pat. No. 7,639,336, which is acontinuation of Ser. No. 10/423,040, filed Apr. 25, 2003 now U.S. Pat.No. 6,876,420, which claims priority to Korean Patent Application Nos.10-2002-0038419 and 10-2002-0035764, filed Jul. 3, 2002 and Jun. 25,2002 respectively, each of which are incorporated by reference for allpurposes as if fully set forth herein.

This is a continuation of U.S. patent application Ser. No. 10/423,040,filed Apr. 25, 2003, which is hereby incorporated by reference. Thisapplication also claims the benefit of Korean Patent Application No.2002-35764 filed in Korea on Jun. 25, 2002, and Korean PatentApplication No. 2002-38419 filed in Korea on Jul. 3, 2002, which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates a liquid crystal display device, and inparticular, to an in-plane switching mode liquid crystal display devicewith improved aperture ratio.

2. Discussion of the Related Art

Recently, with the development of various portable electronic equipmentsuch as mobile phones, PDA's and a notebook computers, demands for flatpanel display devices having light weight, small size and adaptabilityhave correspondingly increased. LCD (liquid crystal displays), PDPs(plasma display panel, FED (field emission displays). VFD (vacuumfluorescent displays), etc. have been actively researched as the flatpanel display devices. Among these the LCD presently the focus in themass production.

The LCD has various display modes according to alignment of liquidcrystal molecules. Among them, a TN (Twisted Nemamic) mode is mainlyused at present because of white-black display easiness, fast responsetime and low driving voltages. In the TN mode liquid crystal displaydevice, when voltage is applied to liquid crystal molecules aligned at asurface of a substrate, the liquid crystal molecules are aligned atright angles to the substrate. Accordingly, when a voltage is applied, aviewing angle is reduced by refractive anisotropy of the liquid crystalmolecules.

In order to solve the above-mentioned viewing angle problem, variousliquid crystal display devices having wide viewing angle characteristicshave been presented. Among them, an in-plane switching mode liquidcrystal display device has been mass-produced. In the IPS mode liquidcrystal display device, when a voltage is applied, viewing anglecharacteristics can be improved by aligning liquid crystal molecules ona plane by forming a horizontal electric field parallel to the plane ofa substrate. FIGS. 1A and 1B show a basic concept thereof.

As depicted in FIG. 1A, in an IPS mode liquid crystal display panel 1, acommon electrode 5 and a pixel electrode 7 are arranged parallel to apixel. When a voltage is not applied to the pixel electrode 7 (there isno signal input), liquid crystal molecules 3 are arranged parallel tothe common electrode 5 and the pixel electrode 7. In more detail, theliquid crystal molecules 3 are aligned at a certain angle to an extendeddirection of the common electrode 5 and the pixel electrode 7. When theliquid crystal molecules 3 are aligned completely parallel with thecommon electrode 5 and the pixel electrode 7, rotational direction ofthe liquid crystal molecules is not definite, and when a gray levelsignal is applied to the pixel electrode 7, aligning of the liquidcrystal molecules is irregular along a whole liquid crystal layer.Accordingly, the actual liquid crystal molecules 3 have to be aligned ata specific angle with respect to the common electrode 5 and the pixelelectrode 7. However, in the drawings, the liquid crystal molecules 3are aligned parallel to the common electrode 5 and the pixel electrode 7for convenience.

As depicted in FIG. 1B, when a voltage (signal) is applied to the pixelelectrode 7 of the liquid crystal display panel 1 in which the liquidcrystal molecules 3 are aligned parallel with the common electrode 5 andthe pixel electrode 7, a horizontal electric field 9 parallel to theliquid crystal display panel 1 occurs between the common electrode 5 andthe pixel electrode 7, and the liquid crystal molecules 3 are rotatedaccording to the horizontal electric field. When a voltage is applied,the liquid crystal molecules 3 are rotated in the same plane accordinglyto the horizontal electric field 9, and accordingly gray inversion dueto refractive anisotropy can be prevented.

FIGS. 2A and 2B show structures of an IPS mode liquid crystal displaypanel, FIG. 2A shows a structure of one pixel in the liquid crystaldisplay panel, and FIG. 2B is a sectional view taken along line I-I′ inFIG. 2A.

As depicted in FIG. 2A, a pixel of the liquid crystal display panel 1 isdefined by a data line 10 and a gate line 20. Only one pixel is shown inFIG. 2A. However, in the actual liquid crystal display panel 1, thereare ‘n’ data lines 10 and ‘m’ gate lines 20, and the n×m-pixels areformed on the whole liquid crystal display panel 1. A thin filmtransistor 11 is formed at a cross region of the data line 10 and thegate line 20 in the pixel. The thin film transistor 11 includes a gateelectrode 18 for receiving a scanning signal from the gate line 20, asemiconductor layer 16 formed on the gate electrode 18 and forming achannel layer by being activated according to the applied scanningsignal, a drain electrode 12 formed on the semiconductor layer 16 andreceiving a picture signal through the data line 10, and a sourceelectrode 14. Accordingly, the thin film transistor 11 applies thepicture signal received from the outside to a liquid crystal layer 50.

In the pixel, a first through third common electrodes 5 a-5 c arrangedparallel to the data line as well as first and second pixel electrodes 7a, 7 b. In addition, a common line 22 contacted to the first throughthird common electrodes 5 a-5 c, and a pixel electrode line 24 contactedto the first and second pixel electrodes 7 a, 7 b are arranged at thecenter of the pixel.

The common electrodes 5 a-5 c and the pixel electrodes 7 a, 7 b are notformed at the same plane. As depicted in FIG. 2B, the common electrodes5 a-5 c are formed on a lower substrate 30 made of a transparent glass,etc., and the pixel electrodes 7 a, 7 b are formed on a gate insulatinglayer 32. In the meantime, because the common electrodes 5 a-5 c and thepixel electrodes 7 a, 8 b are respectively contacted to the common line22 and the pixel electrode line 24, the common line 22 and the pixelelectrode line 24 are respectively formed on the lower substrate 30 andthe gate insulating layer 32.

Not shown in drawings, the gate electrode 18 of the thin film transistoris formed on the substrate 30, and the insulating layer 16 is formed onthe gate insulating layer 32. In addition, the source electrode 12 andthe drain electrode 14 are formed on the semiconductor layer 16. Thecommon electrodes 5 a-5 c and the pixel electrodes 7 a, 7 b formed inthe pixel regions can be respectively formed by a process different fromthat of the thin film transistor, but are usually formed by the sameprocess. The common electrodes 5 a-5 c are formed in a process of thegate electrode 18 of the thin film transistor, and the pixel electrodes7 a, 7 b are formed in a process of the source electrode 12 and thedrain electrode 14. Accordingly, a whole process can be performedquickly.

In the liquid crystal display panel 1, when a scanning signal is appliedto the thin film transistor through the gate line 20, the thin filmtransistor is turned on, a picture signal is transmitted to the pixelelectrodes 7 a, 7 b through the data line 10, a horizontal electricfield parallel to the plane of the substrate occurs between the commonelectrodes 5 a-5 c and the pixel electrodes 7 a, 7 b. Accordingly theliquid crystal molecules are rotated according to the electric fielddirection.

In the meantime, when a picture signal is input to the pixel electrodes7 a, 7 b, an electric field occurs not only between the commonelectrodes 5 a-5 c and the pixel electrodes 7 a, 7 b but also betweenthe pixel electrodes 7 a, 7 b and the data lines 10 a, 10 b. However,because the electric field between the pixel electrodes 7 a, 7 b and thedata lines 10 a, 10 b distorts the whole horizontal electric field, theliquid crystal molecules are not aligned parallel to the substrate.Accordingly, a directional cross talk occurs.

To solve the problem, the first common electrode 5 a has to be arrangedbetween the first pixel electrode 71 and the data line 10 a, and thethird common electrode 5 c has to be arranged between the second pixelelectrode 7 b and the data line 10 b to shield the electric field fromthe data lines 10 a, 10 b. To shield the electric field efficiently, thefirst common electrode 5 a and the third common electrode 5 crespectively abut the data lines 10 a, 10 b. Accordingly, a regionbetween the first common electrode 5 a and the data line 10 a as well asand a region between the third common electrode 5 c and the data line 10b are very small. As a result, the picture of the liquid crystal displaydevice is not displayed in these regions.

On an upper substrate 40, a black matrix 42 and a color filter layer 44are formed. The black matrix 42 prevents light from being leaked to thethin film transistor region and pixels. The color filter layer 44implements an actual color to be formed. A liquid crystal layer 50 isformed between the lower substrate 30 and the upper substrate 40.Accordingly, an IPS mode liquid crystal display panel is completed. Asshown, the black matrix 42 is extended to not only the data lines 10 a,10 b but also the first common electrode 5 a and the third commonelectrode 5 c. Thus, light can be prevented from being leaked to regionsbetween the common electrodes 5 a, 5 c and the data lines 10 a, 10 b.

The IPS mode liquid crystal display device has a lower aperture ratio incomparison with that of a TN mode liquid crystal display device. In theTN mode liquid crystal display device, the pixel electrodes and thecommon electrodes for applying signals to the liquid crystal layer aremade of ITO (indium tin oxide) as transparent metal. In contrast, in theIPS mode liquid crystal display device, the common electrodes 5 a-5 cand the pixel electrodes 7 a, 7 b are made of an opaque metal (gatemetal or source metal). As a result, an aperture ratio is lowered asmuch as regions in which the common electrodes 5 a-5 c and the pixelelectrodes 7 a, 7 b are formed. In particular, because the commonelectrodes 5 a, 5 c are formed abutting on the data lines 10 a, 10 b,the number of common electrodes arranged in one pixel is greater thanthe number of pixel electrodes. Therefore, an aperture ratio is reducedeven more.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an in-plane switchingmode liquid crystal display device that substantially obviates one ormore of the problems due to limitations and disadvantages of the relatedart.

An object of the present invention to provide an in-plane switching modeliquid crystal display device with improved aperture ratio and anincreased light transmittance region.

Another object of the present invention is to provide an in-planeswitching mode liquid crystal display device that easily and efficientlyprovides a regular storage capacitor.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, an in-planeswitching mode liquid crystal display device comprises a substrate; atleast two gate lines disposed on the substrate; at least two data linesdisposed on the substrate crossing the gate lines to define a pixelregion; a driving device disposed in the pixel region; a plurality offirst electrodes disposed in the pixel region; and a plurality of secondelectrodes disposed in the pixel region parallel with the firstelectrodes and at least one first electrode being overlapped with atleast one second electrode, each one of the first electrodes and acorresponding one of second electrodes defining an electric field in adirection parallel to a surface of the substrate.

In another aspect, an in-plane switching mode liquid crystal displaydevice comprises a substrate; at least two gate lines disposed on thesubstrate; at least two data lines disposed on the substrate crossingthe gate lines to define a pixel region; a driving device defined in thepixel region; at least one first line disposed in the pixel region; atleast one second line disposed in the pixel region, the first and secondline defining a first storage capacitor and dividing the pixel regioninto first and second regions; a plurality of first electrodes disposedin the pixel region substantially parallel to the data lines andconnected with the first line; and a plurality of second electrodedisposed in the pixel region substantially parallel to the data linesand connected with the second line, the first and second electrodeshaving at least two overlap regions to define a second storagecapacitor.

In another aspect, an in-plane switching mode liquid crystal displaydevice comprises a plurality of pixel regions defined by plurality ofgate lines crossing with a plurality data lines; a driving device ineach pixel region; and a plurality of first electrodes and secondelectrodes arranged parallel with each other in each pixel region toform an electric field in a plane defining by the crossing gate and datalines, at least two first electrodes and at least two second electrodesbeing overlapped to define a first and second overlap regions, the firstand second overlap regions being symmetric with each other.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIGS. 1A and 1B show a basic concept of an in-plane switching modeliquid crystal display device;

FIGS. 2A and 2B show a structure of the related art in-plane switchingmode liquid crystal display device;

FIGS. 3A and 3B show a structure of an in-plane switching mode liquidcrystal display device in accordance with a first exemplary embodimentof the present invention;

FIG. 4 shows a structure of an in-plane switching mode liquid crystaldisplay device in accordance with a second exemplary embodiment of thepresent invention;

FIG. 5 shows a structure of an in-plane switching mode liquid crystaldisplay device in accordance with a third exemplary embodiment of thepresent invention;

FIG. 6 shows a structure of an in-plane switching mode liquid crystaldisplay device in accordance with a fourth exemplary embodiment of thepresent invention;

FIG. 7 shows a structure of an in-plane switching mode liquid crystaldisplay device in accordance with a fifth exemplary embodiment of thepresent invention;

FIG. 8 shows a mis-alignment occurring in a common electrode or a pixelelectrode of an in-plane switching mode liquid crystal display device inaccordance with the present invention;

FIGS. 9A and 9B show a structure of an in-plane switching mode liquidcrystal display device in accordance with a sixth exemplary embodimentof the present invention;

FIG. 10 shows a structure of an in-plane switching mode liquid crystaldisplay device in accordance with a seventh exemplary embodiment of thepresent invention; and

FIG. 11 shows a structure of an in-plane switching mode liquid crystaldisplay device in accordance with an eighth exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

In general, in an IPS mode liquid crystal display device, lighttransmits through a region between a common electrode and a pixelelectrode. A light transmittance region is varied according to thenumber of common electrodes and pixel electrodes, and a transmittance isgenerally shown as block. For example, in an IPS mode liquid crystaldisplay device depicted in FIGS. 2A and 2B, three common electrodes andtwo pixel electrodes are formed, and there are four light transmittanceregions. Herein, an IPS mode liquid crystal display device having fourtransmittance regions (a 4-block liquid crystal display device) isdescribed but not intended as limiting the present invention to aspecific structure of a liquid crystal display device but rather forconvenience. An IPS mode liquid crystal display device in accordancewith the present invention can be used for not only a 4-block or a6-block or a 8-block IPS mode liquid crystal display device or any otherblock liquid crystal display device. Hereinafter, a specific-block IPSmode liquid crystal display device will be described for convenience,but the present invention is not intended to be limited by this.

In the present invention, by increasing a light transmittance region andeach block region, an aperture ratio of an IPS mode liquid crystaldisplay device can be improved. In particular, by overlapping a commonelectrode with a portion of a pixel electrode, an aperture ratio can beimproved. In the meantime, a storage capacitance is formed at a regionin which the common electrode is overlapped with the pixel electrode. Ingeneral, in the related art IPS mode liquid crystal display device, bymaking a common line and a pixel electrode line overlap with each otherin a pixel, a storage capacitor is formed. Accordingly, to secure a setstorage capacitor, an overlapping region of the common line and thepixel electrode line has to be greater than a certain range, and thecommon line and the pixel electrode line should have a width greaterthan a certain width. However, in the present invention, because aportion of the storage capacitor is formed by overlapping the commonelectrode with the pixel electrode, an overlapping region of the commonline and the pixel electrode line can be reduced. Accordingly, it ispossible to reduce width of the common line and the pixel electrodeline, and an aperture ratio of the liquid crystal display device can befurther improved.

One block is reduced by overlapping the common electrode with the pixelelectrode. For example, in the related art 4-block IPS mode liquidcrystal display device, because one block is removed, it becomes a3-block IPS mode liquid crystal display device. In the related art6-block IPS mode liquid crystal display device, because one block isremoved, it becomes a 5-block IPS mode liquid crystal display device. Asdescribed above, instead of one-decreased block as a light transmittanceregion, light transmittance regions of other blocks are increased.Herein, because the increased light transmittance regions include notonly the light transmittance region of the removed block but also anoverlap region of the common electrode and the pixel electrode, totallight transmittance regions of the liquid crystal display device areincreased. Accordingly, aperture ratio is improved.

Hereinafter, the preferred embodiment of an IPS mode liquid crystaldisplay device in accordance with the present invention will bedescribed in detail with reference to accompanying drawings.

FIG. 3A is a sectional view illustrating an IPS mode liquid crystaldisplay device in accordance with a first exemplary embodiment of thepresent invention, FIG. 3B is a sectional view taken along line II-II′in FIG. 3A. The IPS mode liquid crystal display device is similar to a4-block liquid crystal display device. Actually, however, the IPS modeliquid crystal display device is a 3-block liquid crystal display deviceas shown in FIGS. 3A and 3B, but it is called a 4-block liquid crystaldisplay device like the related art liquid crystal display device fordescriptive purposes. In a liquid crystal display device, a plurality ofdata lines 110 and gate lines 120 are generally arranged to have aplurality of pixels, but, in FIGS. 3A and 3B, only one pixel is shownfor descriptive convenience.

As depicted in FIG. 3A, a thin film transistor is formed at a crosspoint of a data line 110 a and a gate line 120. The thin film transistor111 includes a gate electrode 118 extended from the gate line 120, asemiconductor layer 116 formed on the gate electrode 118, a sourceelectrode 112 extended from the data line 110 on the semiconductor layer116, and a drain electrode 114. In a pixel, there are three parallelcommon electrodes 105 a-105 c and two pixel electrodes 107 a, 107 b. Thefirst through third common electrodes 105 a-105 c are contacted to acommon line 122 arranged in a pixel. First and second pixel electrodes107 a, 107 b are contacted to a pixel electrode line 124 arranged in thepixel.

As depicted in FIG. 3B, the first through third common electrodes 105a-105 c are formed on a first substrate 130 of a transparent materialsuch as glass. The first and second pixel electrodes 107 a, 107 b areformed on a gate insulating layer 132 formed on the first substrate 130.In addition, not shown in FIG. 3B, a gate electrode 118 of the thin filmtransistor 111 is formed on the first substrate 130, a semiconductorlayer 116 is formed on the gate insulating layer 132, and the sourceelectrode 112 and the drain electrode 114 are formed on thesemiconductor layer 134. As described above, the common electrodes 105a-105 c and the gate electrode 118 are formed on the first substrate130, metal such as Cu, Al, Al alloy is laminated by a sputtering or anevaporating method, and is etched as a single layer or plural layers.Herein, it is possible to make common electrodes 105 a-105 c and thegate electrode 118 of different metals. However, it is preferable tomake them of the same metal by the same process.

In addition, the pixel electrodes 107 a, 107 b, the source electrode112, and the drain electrode 114 are respectively formed on thesemiconductor layer 116 and the gate insulating layer 132. The pixelelectrodes 107 a, 107 b, the source electrode 112, and the drainelectrode 114 can be formed by laminating metal such as Cr, Mo, Cu, Al,Al alloy, etc. by a sputtering or an evaporating method and etching themwith an etchant as an etched single layer or plural layers. While it ispossible to make them of the same material by the same process, it isalso possible to make them of different material by different process.

In the meantime, on a second substrate 140 opposed to the firstsubstrate 130, a black matrix 142 for preventing light from being leakedto a region between pixels or a thin film transistor region and a colorfilter layer 144 for implementing an actual color are formed. Then, aliquid crystal layer 150 is formed between the first and secondsubstrates 130, 140 by injecting liquid crystal. In general, the liquidcrystal layer 150 is formed by injecting liquid crystal between thefirst and second substrates 130, 140 adhered with each other by avacuum-injecting process. Also, the liquid crystal layer 150 can beformed by a liquid crystal dispensing process to dispense liquid crystaldirectly onto the first substrate 130 or second substrate 140 beforeadhering the substrates with each other.

In the above-described 4-block IPS mode liquid crystal display device,as depicted in drawings, there are three common electrodes 105 a-105 cand two pixel electrodes 107 a, 107 b in a pixel. Herein, two commonelectrodes, namely, the first and third common electrodes 105 a, 105 care arranged abutting on data lines 110 a, 110 b to minimize electricfield influences from the data lines 110 a, 110 b. In particular, in theIPS mode liquid crystal display device in accordance with the presentinvention, the third common electrode 105 c arranged abutting on thedata line 110 b is overlapped with a portion of the second pixelelectrode 107 b. Because two blocks are united as one block by theoverlap of the third common electrode 105 c and the second pixelelectrode 107 b, the 4-block liquid crystal display device iseffectively changed into a 3-block liquid crystal display device. As aresult, the aperture ratio is improved in accordance with the pertinentoverlap region.

The overlap of the common electrode 105 c and the pixel electrode 107 bgenerates a storage capacitor. In more detail, a storage capacitor isgenerated not only between the common line 122 and the pixel electrodeline 124, but also between the overlapped common electrode 105 c and thepixel electrode 107 b. Accordingly, a storage capacitor required for onepixel is set as a specific value. It is required for the common line 122and the pixel electrode line 124 to generate a storage capacitorcorresponding to a value calculated by subtracting the storage capacitorbetween the overlapped common electrode 105 c and the pixel electrode107 b from the set specific value. Thus, it is possible to decrease thestorage capacitor generated by the common line 122 and the pixelelectrode line 124, and therefore, decrease a width of the common line122 and the pixel electrode line 124. In the related art IPS mode liquidcrystal display device depicted in FIG. 2A, a width of the common line122 is t1. On the other hand, in the IPS mode liquid crystal displaydevice depicted in FIG. 3A, a width of the common line 122 is t2. As aresult, it is possible to obtain width decrease effect as t1-t2. Herein,a width of the common line 122 can be decreased also. In general, thepixel electrode line 124 has a width smaller or greater than that of thecommon line 122, when the pixel electrode line 124 has the same widthwith the common line 122, a width of the pixel electrode line 124 isdecreased also. By the width decrease of the common line (and pixelelectrode line), light transmittance region can be increased.

As described above, the light transmittance region is increased by theoverlap of the common electrode 105 c and the pixel electrode 107 b, anaperture ratio can be improved in comparison with that of the relatedart IPS mode liquid crystal display device. Herein, overlap range of thecommon electrode 105 c and pixel electrode 107 c is not limitedspecifically. In general, because the first and third common electrodes105 a, 105 c arranged abutting on the data lines 110 a, 110 b arerespectively aligned between the first and second pixel electrodes 107a, 107 b, and between the data lines 110 a, 110 b to prevent the datalines 110 a, 119 b from influencing the first and second pixelelectrodes 107 a, 107 b, at least a portion of the third commonelectrode 105 c is arranged between the second pixel electrode 107 b andthe data line 110 b. In consideration of that, it is preferable for thecommon electrode 105 c and the pixel electrode 107 b not to becompletely overlapped with each other. In addition, it is also possibleto have the integer number of common electrodes greater than the numberof pixel electrodes by one.

In FIGS. 3A and 3B, the first through third common electrodes 105 a-105c and the common line 122 are formed on the substrate 130. The first andsecond pixel electrodes 107 a, 107 b and the pixel electrode line 124are formed on the gate insulating layer 132. However, the presentinvention is not limited by that. FIG. 4 illustrates a second exemplaryembodiment of the present invention. It is an IPS mode liquid crystaldisplay device having different structure from the IPS mode liquidcrystal display device shown in FIG. 3.

As depicted in drawings, first through third common electrodes 205 a-205c are formed on a passivation layer 234, first and second pixelelectrodes 207 a, 207 b and a data line 210 are formed on a gateinsulating layer 232. Not shown in drawings, a common line is formed ona first substrate 230 or the passivation layer 234. When the common lineis formed on the first substrate 230, it is preferable for the commonline to be made of the same metal with a gate electrode of a thin filmtransistor. When the common line is formed on the passivation layer 234,it is preferable to be made of the same metal by the same process withthe common electrodes 205 a-205 c. Herein, when the common line isformed on a layer different from the common electrodes 205 a-205 c,namely, the first substrate 230, the common line and the commonelectrodes 205 a-205 c are electrically connected through a contact hole(not shown) formed on the gate insulating layer 232 and the passivationlayer 234.

In the above-described embodiment, because the third common electrode205 c abutting on the data line 210 b is overlapped with the secondpixel electrode 207 b, light transmittance region is increased, andaccordingly an aperture ratio of the IPS mode liquid crystal displaydevice can be improved.

FIG. 5 shows a structure of an in-plane switching mode liquid crystaldevice in accordance with a third exemplary embodiment of the presentinvention. As depicted in FIG. 5, first through a third commonelectrodes 305 a-305 c are formed on a gate insulating layer 332, andfirst and second pixel electrodes 307 a, 307 b are formed on a firstsubstrate 330. Herein, because the third common electrode 305 c isoverlapped with a portion of the second pixel electrode 307 b, anaperture ratio of the liquid crystal display device can be improved.

In the first through third exemplary embodiments of the presentinvention, by increasing light transmittance region by overlapping acommon electrode abutting on a data line with a pixel electrode, anaperture ratio of the liquid crystal display device can be improved.Herein, as depicted in drawings, the common electrodes and the pixelelectrodes can be formed everywhere on a first substrate, a gateinsulating layer and a passivation layer. In the embodiments, positionsof the common electrodes and the pixel electrodes may be embodied inseveral forms without departing from the spirit or essentialcharacteristics thereof, it should also be understood that theabove-described embodiments are not limited by any of the details of theforegoing description, unless otherwise specified, but rather should beconstrued broadly within its spirit and scope as defined in the appendedclaims.

In other words, in the present invention, the common electrodes and thepixel electrodes can be formed on all possible positions (layers). Inaddition, to further improve an aperture ratio, at least one of thecommon electrode and the pixel electrode can be made of ITO (indium tinoxide) or IZO (indium zinc oxide) as transparent metal.

In the meantime, in the IPS mode liquid crystal display device inaccordance with the present invention, overlapped common electrode andpixel electrode are not limited by specific pixel electrode and pixelelectrode. In more detail, in one pixel, any common electrode and pixelelectrode can be overlapped with each other, by the overlap of thecommon electrode and the pixel electrode, an aperture ratio of the IPSmode liquid crystal display device can be improved. In addition, in thepresent invention, it is possible to overlap not less than two commonelectrode and pixel electrode with each other. In the above-describedliquid crystal display device, because only one common electrode andpixel electrode are overlapped with each other, but it is also possibleto overlap not less than one common electrode and pixel electrode witheach other.

FIGS. 6 and 7 respectively show IPS mode liquid crystal display devicesin accordance with fourth and fifth exemplary embodiments of the presentinvention. FIG. 6 shows the liquid crystal display device in which asecond common electrode 405 b is overlapped with a first pixel electrode407 a. FIG. 7 shows the liquid crystal display device in which a firstcommon electrode 505 a is overlapped with a first pixel electrode 507 a.As depicted in the drawings, in the IPS mode liquid crystal displaydevice in accordance with the present invention, all feasible commonelectrodes and pixel electrodes can be overlapped with each other, andaccordingly an aperture ratio of the liquid crystal display device canbe improved.

However, in the liquid crystal display devices in accordance with thefirst through fifth embodiments of the present invention, only a commonelectrode and a pixel electrode arranged on one side of a pixel areoverlapped with each other, following problems can occur.

In the IPS mode liquid crystal display device depicted in FIG. 3A, onlythe third common electrode 105 c and the second pixel electrode 107 barranged on the right side of the pixel are overlapped with each other.Accordingly, an interval between the pixel electrode 107 a and the dataline 110 a in the left side is different from an interval between thepixel electrode 107 b and the data line 110 b in the right side. Eventhe first common electrode 105 a and the third common electrode 105 care respectively arranged around the data lines 110 a, 110 b to shieldthe electric field effect due to the data lines 110 a, 110 b, it isactually impossible to shield the electric field effect completely.Accordingly, there is minute change in the horizontal electric fieldformed in the pixel by the data lines 110 a, 110 b. When an intervalbetween the first common electrode 105 a and the data line 110 a isdifferent from an interval between the third common electrode 105 c andthe data line 110 b, there is a difference between horizontal electricfields in the right and left sides of the pixel. Accordingly, flickermay occur on the display screen.

In the meantime, each construction portion of the liquid crystal displaydevice, for example, the thin film transistor 111, the gate line 120,the data line 110, the common electrode 105 and the pixel electrode 107,etc. are formed by a photo-lithography method. In the photolithography,materials, such as metals, are laminated, and the laminated materialsare etched as a desired pattern using a mask. By the etching processusing the mask, the gate electrode 118, the gate line 120, and thecommon electrodes 105 a-105C of the thin film transistor are formedsimultaneously, and the source electrode 112, the drain electrode 114,the data line 110, and the pixel electrodes 107 a, 107 b aresimultaneously formed. In the etching process, each construction portionis formed by aligning a mask using a maker. Herein, when the maskalignment does not exceed an error limit, a fabricated liquid crystaldisplay device can satisfy a quality standard. However, when the maskalignment exceeds an error limit, a fabricated liquid crystal displaydevice is defective.

However, when misalignment of the mask does not exceed a certain range,the pixel electrodes 107 a, 107 b arranged in the pixel can be minutelyseparated from set positions. In that case, an overlap region of thethird common electrode 105 c and the second pixel electrode 107 b isdecreased or increased in comparison with an overlap region in FIG. 3.FIG. 8 shows an IPS mode liquid crystal display device formed bymis-alignment of the mask. In the IPS mode liquid crystal display devicein FIG. 8, an overlap region of the third common electrode 105 c and thesecond pixel electrode 107 b is decreased by misalignment of the mask(namely, d1>d1′ with d1 being the overlap in FIG. 7), and a storagecapacitor generated by the third common electrode 105 c and the secondpixel electrode 107 b is decreased due to the overlap region decrease.

In the meantime, a storage capacitor in a pixel is set as a specificvalue, and it is calculated by adding a storage capacitor formed by thecommon line 122 and the pixel electrode line 124 to a storage capacitorformed by the common electrodes 105 a-105 c and the pixel electrodes 107a, 107 b. Accordingly, as described above, when a storage capacitor isdecreased due to overlap region decrease of the third common electrode105 c and the second pixel electrode 107 b, a total storage capacitorformed in the pixel is smaller than the set storage capacitor, andaccordingly defection occurs in the liquid crystal display device.

FIGS. 9A and 9B show an IPS mode liquid crystal display device inaccordance with a sixth exemplary embodiment of the present invention.In the liquid crystal display device, it is possible to solve a problemoccurred by overlapping a common electrode with a pixel electrode in oneside.

As depicted in FIG. 9A, the IPS mode liquid crystal display device inaccordance with the sixth embodiment has a similar configuration as theIPS mode liquid crystal display device in FIG. 3A except commonelectrodes 605 a-605 c and pixel electrodes 607 a, 607 b. Accordingly,description about other elements will be abridged, and only the commonelectrodes 605 a-605 c and pixel electrodes 607 a, 607 b will bedescribed. In addition, in the sixth exemplary embodiment, fordescriptive convenience, upper and lower regions centering around acommon line 622 and an pixel electrode line 624 will be separatelydescribed as an A region and a B region.

As depicted in FIG. 9A, in the IPS mode liquid crystal display device inaccordance with the sixth exemplary embodiment, the third commonelectrode 605 c and the second pixel electrode 607 b in the right Aregion are respectively overlapped with a portion of a first commonelectrode 615 a and a first pixel electrode 617 a in the left B region,and a first and a second overlap regions respectively having a d2 widthand a d3 width are formed. Because the first and second overlap regionsactually have the same area with the overlap regions formed in the IPSmode liquid crystal display device in FIG. 3, an equivalent storagecapacitor is generated. Herein, it is possible to reverse left-rightpositions of the common electrodes and pixel electrodes overlapped inthe A and B regions. For example, in the overlap region of the A region,when the common electrode is arranged on the left and the pixelelectrode is arranged on the right, in the overlap region of the Bregion, the common electrode is arranged on the right, and the pixelelectrode is arranged on the left.

As described above, when the overlap regions of the common electrodesand the pixel electrodes are formed on the left and right of the pixelsymmetrically, because an interval between a data line 610 a of thepixel arranged on the left and the first pixel electrode 617 a is thesame with an interval between the data line 610 b of an adjacent pixelarranged on the right and the first pixel electrode 607 b in the Aregion, electric field influences of the data lines 610 a, 610 b affecton the pixel electrodes 607 a, 617 a identically, flicker can beprevented in the IPS mode liquid crystal display device.

In the meantime, in the photo-lithography process (pixel electrode orcommon electrode process), when a minute mis-alignment of the maskoccurs, the pixel electrode or the common electrode is deviated from aset position, overlap region of the common electrode and the pixelelectrode is changed. FIG. 9B shows an IPS mode liquid crystal displaydevice in a mask mis-alignment state. In the IPS mode liquid crystaldisplay device shown in FIG. 9B, pixel electrodes 607 a, 607 b, 617 a,617 b are deviated from set positions due to the mask mis-alignment, thepixel electrodes 607 a, 607 b, 617 a, 617 b are moved to the left.

As depicted in FIG. 9B, by the movement of the pixel electrodes 607 a,607 b, 617 a, 617 b, the third common electrode 605 c and the secondpixel electrode 607 b in the A region form a first overlap region havinga d2′ width, and the first common electrode 615 a and the first pixelelectrode 617 a forms a second overlap region having a d3′ width.Herein, d2′ is smaller than d2 in FIG. 9A (d2′<d2) by the movement ofthe pixel electrode 607 b to the left, and d3′ is greater than d3(d3′>d3). Because the pixel electrodes 607 a, 607 b, 617 a, 617 b movethe same distance in the pixel, width decrease value (d2′−d2) in thefirst overlap region is the same with width increase of the secondoverlap region (d2′−d2=d3′−d3). Accordingly, although the pixelelectrode (or the common electrode) is minutely moved by the maskmis-alignment, the sum total of the first overlap regions and the secondoverlap region is maintained constant (namely, d2+d3=d2′+d3′) so thatthe storage capacitor generated by the overlap regions 608, 618 ismaintained constant.

As described above, in the embodiment, by symmetrically overlapping thecommon electrode with the pixel electrode on the left and right sides inthe pixel, an interval between the data line and the pixel electrode isalways maintained uniformly. Thus, electric field influence by the dataline can be maintained uniformly even though displacement occurs in aposition of the pixel electrode or the common electrode by the maskmis-alignment. By uniformly forming a storage capacitor, it is possibleto prevent defection of the IPS mode liquid crystal display device.

In the meantime, there is no limitation in determining of a commonelectrode and a pixel electrode overlapped with each other in a pixelsymmetrically. If overlap regions are formed symmetrically in the pixel,any common electrode and pixel electrode arranged in the pixel can beoverlapped.

FIG. 10 shows an IPS mode liquid crystal display device in accordancewith a seventh exemplary embodiment of the present invention. Asdepicted in FIG. 10, a common electrode and a pixel electrode areoverlapped with each other in an A region and a B region dividedcentering around a common line 722 and a pixel electrode line 724.However, different from the IPS mode liquid crystal display devicedepicted in FIG. 9A, in the IPS mode liquid crystal display device inaccordance with the seventh exemplary embodiment, a second commonelectrode 705 b is overlapped with a second pixel electrode 707 b in theA region, and a first overlap regions is formed. In the B region, thesecond common electrode 706 b is overlapped with a first pixel electrode707 a, and a second overlap region is formed. Herein, the first andsecond overlap regions 708, 718 are symmetrically formed in the pixel.Hence, even if the mask is mis-aligned in the photo-lithography process,a storage capacitor can be uniformly formed. Accordingly, the IPS modeliquid crystal display device in accordance with the seventh exemplaryembodiment can have the same effect with the IPS mode liquid crystaldisplay device depicted in FIG. 9A.

In addition, the IPS mode liquid crystal display device in accordancewith the present invention is not limited by 4-block (formed of threecommon electrodes and two pixel electrodes) liquid crystal displaydevice, but it can be applied to various block types liquid crystaldisplay device. FIG. 11 shows an IPS mode liquid crystal display devicein accordance with an eighth exemplary embodiment of the presentinvention. It shows a structure of a 6-block (formed of four commonelectrodes and three pixel electrodes) liquid crystal display device.Herein, FIG. 11 shows the liquid crystal display device in which commonelectrodes 805 a-805 d are overlapped with pixel electrodes 807 a-807 casymmetrically. However, the embodiment can be also applied to a liquidcrystal display device in which the common electrodes 805 a-805 d areoverlapped with the pixel electrodes 807 a-807 c symmetrically. In the6-block (actually 5-block) IPS mode liquid crystal display device,because at least one common electrode 805 d and the pixel electrode 807c can be overlapped with each other, light transmittance region in thepixel is increased, and an aperture ratio of the liquid crystal displaydevice can be improved.

As described above, in the IPS mode liquid crystal display device inaccordance with the present invention, by overlapping at least onecommon electrode with a pixel electrode in a pixel, light transmittanceregion in the pixel is increased, and an aperture ratio of the liquidcrystal display device can be improved. In addition, in the IPS modeliquid crystal display device in accordance with the present invention,by forming an overlap region of a common electrode and a pixel electrodein a pixel symmetrically, electric field effect of a data line can bemaintained uniformly along the total pixels. Thus, flicker can beprevented in the IPS mode liquid crystal display device. Furthermore, inthe IPS mode liquid crystal display device in accordance with thepresent invention, even if there is displacement in position forming ofa common electrode and a pixel electrode, by always uniformlymaintaining the overlap region, a storage capacitor of the pixel can bemaintained uniformly.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the apparatus and method ofgenerating gamma voltage of the present invention without departing fromthe spirit or scope of the invention. Thus, it is intended that thepresent invention cover the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

1. A method of fabricating an in-plane switching mode liquid crystaldisplay device, comprising: providing a substrate; forming at least twogate lines on the substrate; forming at least two data lines on thesubstrate and crossing the gate lines to define a pixel region; forminga driving device in the pixel region; forming at least one first line inthe pixel region; forming at least one second line in the pixel region,the first and second lines defining a first storage capacitor anddividing the pixel region into first and second regions; forming aplurality of first electrodes in the pixel region substantially parallelto the data lines and connected with the first line; and forming aplurality of second electrodes in the pixel region substantiallyparallel to the data lines and connected with the second line, the firstand second electrodes each having at least two overlap regions to definea second storage capacitor, wherein the two overlap regions aresymmetric with each other and a sum total of the first overlap regionand the second overlap region is constant with respect to a maskmis-alignment during formation.
 2. The method according to claim 1,wherein the first line is formed to define a common electrode line, andthe second line defines a pixel electrode line.
 3. The method accordingto claim 1, wherein the first electrodes form at least a portion of acommon electrode, and the second electrodes form at least a portion of apixel electrode.
 4. The method according to claim 1, wherein acapacitance of the second storage capacitor is constant with respect tothe mask mis-alignment during formation.
 5. The method according toclaim 1, wherein at least one of the first electrodes is formedsubstantially abutting the data line.
 6. The method according to claim1, wherein the number of the first electrodes is one greater than thenumber of the second electrodes.
 7. The method according to claim 1,wherein the driving device is formed to include a thin film transistor.8. The method according to claim 7, wherein the thin film transistorincludes: a gate electrode disposed on the substrate; an insulatinglayer disposed on the substrate; a semiconductor layer disposed on theinsulating layer; a source electrode disposed on the semiconductor layerin electrical contact with the semiconductor layer; a drain electrodedisposed on the semiconductor layer in electrical contact with thesemiconductor layer; and a passivation layer over the substrate havingthe semiconductor layer, source electrode, and the drain electrode. 9.The method according to claim 8, wherein one of the first electrodes isformed on one of the insulating layer and the passivation layer.
 10. Themethod according to claim 7, wherein one of the second electrodes isformed on one of the insulating layer and the passivation layer.
 11. Themethod according to claim 1, wherein positions of one of the firstelectrodes and the second electrode are alternated in the each of firstand second regions.